the boat operates when requested. Wallasea island was created from five smaller islands by building sea defences, and was largely used for grazing sheep until the 1930s, when it was drained to provide arable land. In 2006, the Department for Environment, Food and Rural Affairs (DEFRA) created of new saltmarsh and intertidal mud flats. Since 2008, a project managed by the Royal Society for the Protection of Birds (RSPB) to transform more of the island back to intertidal coastal marshland has been ongoing, helped by spoil from the excavation of tunnels for the Crossrail project, which has been used to raise the level of parts of the island. Breaches were then made in the sea walls, to create some of intertidal habitat. In order to deliver over 3 million tonnes of earth, Crossrail built a temporary jetty in the river, where ships arrived between August 2012 and March 2015, and the sea walls were breached on 11 July 2015. The original plans involved a further 8 million tonnes of soil, but the RSPB were unable to source this, and so a revised scheme was implemented, where sea water was admitted to shallow lagoons through an existing sluice in the sea wall. The river continues eastwards, and is joined by the River Roach at the eastern end of Wallsea Island. It flows into the North Sea between Holliwell Point () and Foulness Point () on its north and south banks respectively. High water at Burnham is one hour and ten minutes later than high water at Dover, with a tidal range of at spring tides and at neap tides. Approaching the river from the North Sea requires care, as the Whitaker Channel and Ray Sand Channel are separated by a large sandbank known as Buxey Sand, and to the south of the Whitaker Channel, the Foulness Sands are a danger area, used as a military firing range. History There was a proposal in 1825 to extend navigation onwards from Battlesbridge to Purfleet with a branch to Billericay. The route to Billericay would have been around long, and 29 locks were proposed, in order to negotiate the difference in height of . Because the river is still tidal at Battlesbridge, a sea lock would have provided access from the river, with five locks soon afterwards. A further seven locks would have been constructed along the route, with a flight of 16 locks